1. Field of the Invention
The present invention relates to a method of and an apparatus for performing switching between two different power supplies around their synchronous point with no interruption, using an overlap-type change-over switch which performs switching between the power supplies after connecting both of them simultaneously for a given time period.
2. Description of the Prior Art
In a conventional uninterruptible power supply unit or the like which performs switching between two different power supplies with no interruption, an automatically-synchronizing closing device has been used which achieves switching between the power supplies by executing adjustments in voltage value and phase between the power supplies so as to ensure precise synchronization therebetween.
Accordingly, the foregoing conventional automatically-synchronizing closing device is provided with functions of executing the voltage value and frequency controls, which, however, inevitably render the device complicated in structure and thus expensive.